Summary: In anticipation of programatic needs, we have been developing in vitro methods for measuring neutralization of hepatitis C virus. Hepatitis C virus vaccines have already been proposed. In order to easily evaluate them, an in vitro assay of neutralization will be necessary as opposed to testing in the chimpanzee model. Hepatitis C virus grows poorly in cell culture and its replication is difficult to measure. We investigated a new cell culture system described fro Russia and determined that it was inadequate to fulfill our needs. We have developed a real time RT-PCR system based on the TaqMan method that improves the senstivity and reproducibility of TaqMan in order to be able to follow the HCV infection in our experimental animals. This method could also be applied to patients. We have also developed ELISA assays for antibody to the envelope glycoproteins of HCV and for several of the non-structural proteins. These assays will be suefull in vaccine evaluation.